Title

Author

Date

June 2013

Document Type

Thesis

Degree Name

M.S.

Institution

Oregon Health & Science University

Abstract

Patients with overt thyroid disease have altered metabolic function. It is not clear whether metabolic function varies with normal thyroid function as measured by serum thyroid stimulating hormone (TSH) concentration. To address this gap in clinical knowledge, a cross-sectional study was carried out to determine the relationship between serum TSH concentrations within the normal range and markers of body composition, energy expenditure, and macronutrient oxidation in healthy control and euthyroid L-T4 treated women. Participants (n=65) were divided into low-normal (0.34 - 2.49 mU/L, n = 46) and high-normal (2.50 - 5.60 mU/L, n = 19) TSH concentration groups. Total energy expenditure by doubly labeled water, resting energy expenditure and thermic effect of food by indirect calorimetry, and body composition by DEXA were measured. Macronutrient oxidation rates were calculated using standard equations. Means and differences in means of body composition and energy expenditure variables and macronutrient oxidation rates between groups were compared using independent t-tests and linear regression models and across TSH as a continuous variable. The average weight was significantly lower in the low-normal than the high-normal TSH group (72.7 Â± 15.3 vs. 82.2 Â± 22.3 kg, p=0.05) as was BMI (27.1 Â± 5.4 vs. 30.5 Â± 8.0 kg/m[superscript 2], p=0.05). No other differences between groups or relationships with TSH were observed. In conclusion, we found no associations between variations in TSH concentration within the established normal range and differences in body composition, energy expenditure or macronutrient oxidation parameters.

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